Disconnect terminal board

ABSTRACT

A disconnect terminal board includes a bridging contact attached to an axially movable insulating plunger and adapted to engage a pair of spaced-apart stationary contacts. The plunger extends through an aperture in a guide member, and it is spring biased to a disconnected position in which it protrudes from the guide member, thereby visually indicating the disconnected state. The plunger includes a rotatable locking portion which cooperates with stationary clamping means to retain the plunger in a connected position upon moving the plunger against the spring bias to carry the bridging contact into engagement with the stationary contacts and then rotating the locking portion to a locked position.

Fisher 1 1 [11 I 3,813,642 May28, 1974 l DISCONNECT TERMINAL BOARD [75] Inventor: William M. Fisher, Springfield, Pa.

[73] Assignee: General Electric Company,

Philadelphia, Pa.

22 Filed: Feb. 9, 1973 21 App1.No.:330,990

[52] US. Cl 339/198 R, 339/19, 200/16 A [51] Int. Cl HOlr 9/08 [58] Field of Search 339/198 R, 19, 222; 200/16 A, 158

[56] References Cited UNITED STATES PATENTS 1,157,960 10/1915 Post 200/16 A 2,064,736 12/1936 Dahl 200/158 2,659,838 11/1953 Du Rocher 200/16 A" 2,854,552 9/1958 Governeur 200/166 PC 2,930,859 3/1960 Nolden et al.. 200/16 A 2,951,916 9/1960 Scheffer 200/16 A 3,164,709 1/1965 Gentile 339/198 3,657,503 4/1972 Smith..... 339/222.X

Primary ExaminerBobby R. Gay

Assistant Examiner-Robert A. Hafer Attorney, Agent, or FirmJ. Wesley Haubner; Albert S. Richardson, Jr.

[57] ABSTRACT A disconnect terminal board includes a bridging contact attached to an axially movable insulating plunger and adapted to engage a pair of spaced-apart stationary contacts. The plunger extends through an aperture in a guide member, and it is spring biased to a disconnected position in which it protrudes from the guide member, thereby visually indicating the discon- =nected state. The plunger includes a rotatable locking portion which cooperates with stationary clamping meansto retain the plunger in a connected position upon moving the plunger against the spring bias to carry the bridging contact intoengagement with the stationary contacts and then rotating the locking portion to a locked'position.

9 Claims, 5 Drawing Figures 1 DISCONNECT TERMINAL BOARD BACKGROUND AND OBJECTS OF THE INVENTION This invention relates generally to electrical terminal boards, and more particularly it relates to terminal boards equipped with convenient disconnecting means.

more terminals of external wires. A conductor joins the two contacts of each pair, thereby interconnecting the respective wires whose terminals are fastened thereto. The terminal board serves as an interface between two different sets of wires which are respectively associated with interdependent electric. apparatus or circuits. For example, the wires of one set may be associated with the secondaries of instrument transformers and the control circuits of a circuit breaker in a power delivery system, whereas the wires of the other set may be connected to the circuits of a protective relay.

Once two circuits have been interconnected by fastening the respective wires to a terminal board, it is sometimes desirable, for purposes of testing, servicing,

calibrating, Orthe like, to be able to disconnect the circuits at this interface without disturbing any wiring.

Toward that end, appropriate disconnecting means are needed. One prior art approach has been to provide, in conjunction with a standard terminal board, separate auxiliary switches or a test block comprising an array of single-pole knife'switches. Another prior art practice has been to equip the terminal board itself with interconnecting conductors which include a removable link or separable sliding links. However, all of the commercially available disconnect terminal boards thatl am presently'aware of have certain shortcomings with respectto safety,reliability, or economy. I Accordingly, it is'a-general objective of my invention to provide an improved disconnect terminal board.

A more specific object of the. invention is to provide a relatively inexpensive and compact terminalboard which includes convenient switching means for reliably connecting and for safely disconnecting'the contacts.

SUMMARY OF THE INVENTION the plunger to the latter position. The aforesaid locking portion of the plunger, in cooperation with fixedly located clamping means, is disposed for rotary movement between released and locked positions. Attached to the plunger is a bridging contact which is carried thereby into engagement with both of the stationary contacts when the plunger is moved axially from its disconnected position toward its connected position. With the bridging contact engaging the stationary contacts the aforesaid clamping means is actuated by rotating the locking portion of the plunger from released to locked positions so as to retain the plunger in its connected position wherein the bridging contact is firmly held against the stationary contacts. This insures a reliable and trouble free connection between the external wires whose terminals are respectively fastened to the stationary contacts. Upon rotation of the locking portion of the plunger to its released position, the force of the resilientmeans moves the plunger to its disconnected position wherein the bridging contact engages the guide member, thereby preventing further withdrawal of the plunger from the aperture in the guide member. Whenever the plunger is'observed in its disconnected position, the observer knows that the stationary contacts are positively disconnected.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 terminal board to illustrate the relative free movement of the bridging contact which is carried thereby; and

FIG. 5 is a partial sectional view, similar to FIG. 3 but with the bridging contact in a slightly tilted disposition.

DESCRIPTION OF THE PREFERRED I EMBODIMENT With reference now to FIG. 1, my disconnect terminal board 1 is seen to comprise a base member 8 made of insulating material and having a planar surface 8a on which are mounted, in sideby-side relationship, a plurality of pairs of spaced-apart relatively stationary electric contacts. As viewed in FIG. 1, only thenear-side contact 2a, 3a, 4a, 5a, 6a, and 7a of each pair can be seen, and it will be understood that the other contacts forming these pairs are located on the far side of the terminal board.

. As is best seen in FIG. 2, which illustrates the pair of stationary contacts 3a and 3b, these contacts include suitable means 10 and 12 for fastening thereto the terminals of external wires (not shown). The means referred to are internally threaded metal tubes whose ends are spread to affix the planar portions 9 and 11 of contacts 3a and 3b to the base member 8. The wire terminals can be fastened to the contacts by conventional terminal screws'or, alternatively, by nuts on threaded posts which in turn are inserted in the tubes 10 and 12.

In order to ensure electrical isolation of each pair of stationary contacts, adjacent pairs of contacts are re-- riers and walls, and hence above the pairs of stationary contacts, there is supported an insulating marker strip and guide member 19. This guide member has a plurality of apertures which are centered between the stationary contacts ,of the respective pairs of contacts. The aperture which is centered between the contacts 3a and 3b is shown at in FIG. 2.

in accordance with my invention, the terminal board 1 includes novel means for connecting and disconnecting the two contacts of each pair of stationary contacts. More particularly,'the connecting and disconnecting means comprises a plurality of elongated plungers 21, 22, 23, 24, 25, and 26 which respectively extend through the apertures in the guide member 19 where they are disposed for axial movement between connected and disconnected positions. Each of these plungers comprises a cylindrical body 27 of insulating material. At the distal end of the plunger (i.e., the end farthest from the base member 8) there is an annular flange 29 and a knurled, slotted knob 30 which is inserted in the body 27. Attached to the other end of each plunger is a nonrotatable bridging contact adapted to engage and thereby electrically interconnect the planar portions of the associated pair of stationary contacts. As is illustrated in FIGS. 2, 4, and 5 for plunger 22, the bridging contact comprises a flat metal member 31 carried loosely by the plunger in a plane substantially perpendicular to the axis of the plunger but with freedom to tilt slightly upon engaging the associated stationary contacts.

Resilient means in the form of helical springs 21a, 22a, 23a, 24a, 25a, and 26a are provided for moving the respective plungers 21-26 axially to their disconnectedpositions. Each of these helical springs encircles the corresponding plunger between its flange 29 and the guidemember 19. The plunger 22 is shown in its disconnected position in H6. 2 where it will be observed that the bridging contact 31 has been carried into engagement with the guide member 19 to prevent further withdrawal of the plunger from the aperture 20. In this manner the plunger, while being free to move axially between its connected and disconnected positions, is captured in the terminal board.

When a plunger is moved axially against the force of the helical spring toward its connected position, the attached bridging contact is carried into engagement with both of the stationary contacts of the associated pair. The plunger can be releasably locked in its connected position by the interaction of a rotatable locking portion of the plunger and cooperating clamping means which is fixedly located with respect to the base member. The rotatable locking portion can take any one of a variety of suitable formshln the illustrated embodiment of my invention it comprises a threaded section of the plunger. Preferably this section is an externally threaded metal insert 28 affixed to the end of theinsulating body 27 nearest-to the base member, and it can be rotated between released and locked positions by appropriately turning the knob at the other end of the same plunger.

The cooperating clamping means preferably comprises a tubular metal insert 13 located in a portion of the base member midway between the spaced-apart stationary contacts and in register with the corresponding aperture in the guide member 19. The insert 13 has internal threads adapted to mate with the threaded section 28 of the associated plunger when the latter is rotated from its released position to its locked position. Consequently the clamping means is actuated by rotating the plunger from released to locked positions with the bridging contact engaging the associated pair of stationary contacts, and this retains the plunger in its connected position wherein it firmly holds the bridging contact against the stationary contacts. FIG. 3 illustrates the plunger 24 locked in its connected position, with the helical spring 240 compressed and the bridging contact 33 firmly held in engagement with both of the contacts 5a and 5b of the associated pair of stationary contacts. It will now be appreciated that although the illustrated structure is of relatively small size it yields a highly reliable electrical connection.

Because of its freedom to tilt slightly, the movable bridging contact is able to establish a good electrical connection between the spaced-apart stationary contacts of the terminal board even if the planar portions of the latter are not perfectly aligned with each other. This is illustrated in FIG. 5 where the plunger 22 is shown in its connected position with its locking portion 28 screwed tightly into the clamping means 13. The bridging contact 31 is slightly tilted but nevertheless firmly held against both of the non-coplanar parts 9 and 11 of the stationary contacts 3a and 312. To accomplish thisresult, the bridging contact is preferably located on an undercut portion 32 of the externally threaded insert 28 which portion has an axial length more than twice the thickness of the separate bridging contact (see FIG. 2). The degree of tilting freedom is illustrated by the phantom lines in FIG. 4. This loose mounting also promotes relative rotational freedom between the bridging contact and the plunger when the latter is turned while the bridging and stationary contacts are engaged.

One of the advantages of a disconnect terminal board constructed in accordance with my invention is that whenever the locking portion of a plunger is rotated to its released position by unscrewing the threaded section 28 from the cooperating insert 13, the plunger is immediately and automatically biased in an axial direction to its disconnected position by the associated helical spring, and in its disconnected position the plunger itself serves as a clear visual indication that the associated pair of stationary contacts are positively disconnected. Thus a person observing the terminal board as it has been illustrated in FIG. 1 is immediately aware that the pairs of stationary contacts respectively associated with the protruding plungers 21, 22, and 26 are disconnected and that the pairs of stationary contacts respectively associated with the depressed plungers 23, 24, and 25 are connected. in order to change the position of a plunger, a workman can conveniently manipulate the same by grasping its knurled knob 30 with his fingers or by using a screwdriver in the slotted face of the knob. This operation does not expose the workman to the electrical potential of the stationary contacts because the knob 30 is isolated therefrom by the insulating body 27 of the plunger and by the insulating guide member 19 and barriers 14-18.

Another advantage of a disconnect terminal board constructed in accordance with my invention is that except for the disconnecting means the terminal board is built from standard parts which are interchangeable with the parts of conventional terminal boards. lf desired, the disconnecting means can be utilized with only selected pairs of stationary contacts, with the contacts contacts 3a and 3b shown in FIG. 2 could be interconnected by a fixed electroconductive link spanning the space therebetween, or alternatively they could be replaced by a single, integral'stationary contact.

A disconnect terminal board having all of the features illustrated in the drawing and described hereinbefore is relatively compact in size and economical to make, yet it is versatile and highly reliable in operation. The disconnecting and connecting operations can be performed quickly, conveniently, and with safety. When the locking portion of a plunger is rotated to its released position, the plunger is spring biased to its disconnected position which serves as a visual indication that the associated pair of stationary contacts are positively disconnected. All of the movable parts of the disconnecting means are captured in the terminal board to prevent their separation and possible loss. The combination of all of these attributes in a unitary structure is believed to beunique in the art of disconnect terminal boards.

While l have shown and described a particular embodiment of my invention by way of example, it will be obvious to persons skilled in the art that various changes and modifications may be made without departing from my inventive concept. I therefore intend to cover by the concluding claims all such changes and modifications which fall within the true spirit and scope of my invention.

What I claim is new and desire to secure by Letters Patent of the United States is:

l. A disconnect terminal board comprising:

a. a base member of insulating material;

b. at least one pair of spaced-apart stationary electric contacts mounted on said base member, said contacts respectively including means for fastening thereto the terminals of external wires;

c. a guide member of insulating material supported by said base member above said stationary contacts, said guide member having at least one aperture which is centered between said stationary contacts;

d. an elongated plunger extending through the aperture of said guide member, said plunger having an insulating body disposed for axial movement between connected and disconnected positions and having a locking portion disposed for rotary movement between released and locked positions;

e. resilient means for moving said plunger axially to its disconnected position;

f. a bridging contact carried by said plunger and movable into engagement with both of said stationary contacts when said plunger is moved axially against the force of said resilient means toward said connected position; and

g. clamping means, actuated by rotation of the locking portion of said plunger from its released position to its locked position with said bridging contact engaging said stationary contacts, for retaining said plunger in its connected position wherein it firmly holds said bridging contact against said stationary contacts.

2. The terminal board of claim 1 wherein said locking portion comprises a threaded section of said plunger and said clamping means is fixedly located with respect to said base member and has theads that are adapted to mate with said threaded section when the latter is rotated from said released position to said locked position, and wherein said bridging contact is a separate fiat member carried by said plunger with rotational free- 5 dom relative to said threaded section.

3. The terminal board of claim 1 wherein said locking portion comprises external threads on the end of said plunger nearest to said base member and said clamping means comprises a threaded portion of said base member between said stationary contacts, said threaded portion registering with said aperture and having internal threads that are adapted to mate with said external theads when said plunger is rotated from said released position to said locked position.

4. The terminal board of claim 3 wherein said threaded portion of said base member comprises a threaded metal insert.

5. The terminal board of claim 1 wherein said bridging contact is a flat metal member carried by said plunger in a plane substantially perpendicular to the axis of the plunger but with freedom to tilt slightly upon engaging said stationary contacts.

6. The terminal board of claim 5 wherein said plunger comprises a cylindrical body of insulating material.

7. The terminal board of claim 1 wherein said bridging contact is attached to said plunger and is carried thereby into engagement with said guide member when the plunger is moved to its disconnected position by said resilient means whereby further withdrawal of said plunger from said aperture is prevented.

8. The terminal board of claim 1 wherein said resilient means comprises a helical spring encircling said plunger between said guide member and the end of said plunger farthest from said base member.

9. A disconnect terminal board comprising:

a. a base member of insulating material;

b. a plurality of pairs of spaced-apart stationary electric contacts mounted side-by-side on said base member, said contacts respectively including means for fastening terminals of external wires thereto;

0. a guide member of insulating material supported by said base member above said stationary contacts, said guide member having a plurality of apertures which are respectively centered between the stationary contacts of selected pairs of contacts; and

d. means for connecting and disconnecting the stationary contacts of said selected pairs comprising, for each of said apertures,

i. an elongated plunger of insulating material extending through the corresponding aperture of said guide member, said plunger being disposed for axial movement between connected and disconnected positions and having a locking portion disposed for rotary movement between released and locked positions,

ii. resilient means for moving said plunger axially to its disconnected position,

iii. a bridging contact carried loosely by said plunger into engagement with both of the stationary contacts of the associated pair when said plunger is moved axially against the force of said resilient means toward said connected position, said bridging contact having freedom to tilt slightly and to rotate relative to said locking por- 7 8 tion of the plunger upon engaging said stationary contact engaging said stationary contacts, for recontacts, and taining said plunger in its connected position iv. clamping means, actuated by rotation of the wherein it firmly holds said bridging contact locking portion of said plunger from its released against the associated pair of stationary contacts.

position to its locked position with said bridging 

1. A disconnect terminal board comprising: a. a base member of insulating material; b. at least one pair of spaced-apart stationary electric contacts mounted on said base member, said contacts respectively including means for fastening thereto the terminals of external wires; c. a guide member of insulating material supported by said base member above said stationary contacts, said guide member having at least one aperture which is centered between said stationary contacts; d. an elongated plunger extending through the aperture of said guide member, said plunger having an insulating body disposed for axial movement between connected and disconnected positions and having a locking portion disposed for rotary movement between released and locked positions; e. resilient means for moving said plunger axially to its disconnected position; f. a bridging contact carried by said plunger and movable into engagement with both of said stationary contacts when said plunger is moved axially against the force of said resilient means toward said connected position; and g. clamping means, actuated by rotation of the locking portion of said plunger from its released position to its locked position with said bridging contact engaging said stationary contacts, for retaining said plunger in its connected position wherein it firmly holds said bridging contact against said stationary contacts.
 2. The terminal board of claim 1 wherein said locking portion comprises a threaded section of said plunger and said clamping means is fixedly located with respect to said base member and has theads that are adapted to mate with said threaded section when the latter is rotated from said released position to said locked position, and wherein said bridging contact is a separate flat member carried by said plunger with rotational freedom relative to said threaded section.
 3. The terminal board of claim 1 wherein said locking portion comprises external threads on the end of said plunger nearest to said base member and said clamping means comprises a threaded portion of said base member between said stationary contacts, said threaded portion registering with said aperture and having internal threads that are adapted to mate with said external theads when said plunger is rotated from said released position to said locked position.
 4. The terminal board of claim 3 wherein said threaded portion of said base member comprises a threaded metal insert.
 5. The terminal board of claim 1 wherein said bridging contact is a flat metal member carried by said plunger in a plane substantially perpendicular to the axis of the plunger but with freedom to tilt slightly upon engaging said stationary contacts.
 6. The terminal board of claim 5 wherein said plunger comprises a cylindrical body of insulating material.
 7. The terminal board of claim 1 wherein said bridging contact is attached to said plunger and is carried thereby into engagement with said guide member when the plunger is moved to its disconnected position by said resilient means whereby further withdrawal of said plunger from said aperture is prevented.
 8. The terminal board of claim 1 wherein said resilient means comprises a helical spring encircling said plunger between said guide member and the End of said plunger farthest from said base member.
 9. A disconnect terminal board comprising: a. a base member of insulating material; b. a plurality of pairs of spaced-apart stationary electric contacts mounted side-by-side on said base member, said contacts respectively including means for fastening terminals of external wires thereto; c. a guide member of insulating material supported by said base member above said stationary contacts, said guide member having a plurality of apertures which are respectively centered between the stationary contacts of selected pairs of contacts; and d. means for connecting and disconnecting the stationary contacts of said selected pairs comprising, for each of said apertures, i. an elongated plunger of insulating material extending through the corresponding aperture of said guide member, said plunger being disposed for axial movement between connected and disconnected positions and having a locking portion disposed for rotary movement between released and locked positions, ii. resilient means for moving said plunger axially to its disconnected position, iii. a bridging contact carried loosely by said plunger into engagement with both of the stationary contacts of the associated pair when said plunger is moved axially against the force of said resilient means toward said connected position, said bridging contact having freedom to tilt slightly and to rotate relative to said locking portion of the plunger upon engaging said stationary contacts, and iv. clamping means, actuated by rotation of the locking portion of said plunger from its released position to its locked position with said bridging contact engaging said stationary contacts, for retaining said plunger in its connected position wherein it firmly holds said bridging contact against the associated pair of stationary contacts. 